Seamless metal tubing also known as seamless mechanical tubing has outside diameters ranging from 1/8 inch to 103/4 inches and wall thicknesses ranging from 20 gauge to 2 inches. The tubing may be oval, square, rectangular or other special shape in cross-section obtainable in various sizes and wall thicknesses. Mechanical tubing is available either hot finished or cold drawn but furnished (principally) cold drawn and is adaptable to varied treatment by expansion, cupping, tapering, swaging, flanging, coiling, welding and similar manipulations. Seamless metal tubing has a number of uses as aircraft tubing and automobile components. Small diameter seamless steel tubing is used by way of example on automotive brake lines.
Seamless carbon-steel tubing is expensive to produce and is made in finite lengths principally by heating a round metal ingot, punching a hole in the ingot and working the so punched ingot into a tube of selected length, diameter and wall thickness.
A method of making continuous seamless tubing is disclosed in DE 3034792 dated Sept. 16, 1980. The continuous manufacturing is in a single production line that includes melting, casting, machining, drawing and shearing stations. In this process a bath of molten metal is required from which it can be drawn in the form of a continuous seamless tubing. Considerable heat is required to maintain a molten bath and from which there is substantial heat losses.
Another means of forming a tube is by seam welding as disclosed in U.S. Pat. No. 3,248,512 issued Apr. 26, 1966 to R. A. Sommer. This patent discloses the use of induction heating with selective concentration of the heating to melt the material of abutting edges downwardly from the point of convergence and wherein there is pressural contact of such abutting edges. The end product is a welded seam tube.